Composite material with improved structural, acoustic and thermal properties

ABSTRACT

A method of forming a multilayer insulation material formed of an acoustical composite layer and a first thermal layer is provided. The acoustical and insulting layer is formed of a polymer based thermoplastic material and reinforcing fibers. Preferably the reinforcing fibers are wet use chopped strand glass fibers (WUCS). The acoustical composite layer may be formed by opening the WUCS fibers, blending the reinforcement and polymer fibers, forming the reinforcement and polymer fibers into a sheet, and then bonding the sheet. A first thermal layer formed of one or more polymer based thermoplastic organic materials is then positioned on a first major surface of the acoustical composite layer. A second thermal layer of polymeric fibers may be optionally positioned on a second major surface of the acoustical composite layer. The multilayer acoustic material may be utilized in semi-structural and acoustical applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/688,013 entitled “Development Of Thermoplastic CompositesUsing Wet Use Chopped Strand Glass In A Dry Laid Process” filed Oct. 17,2003, the content of which is incorporated by reference in its entirety.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention relates generally to acoustical products, and moreparticularly, to a method of forming a thermal and acoustic compositematerial that includes a first layer of polymer based thermoplasticfibers and glass fibers and a second layer of organic fibers.

BACKGROUND OF THE INVENTION

Sound insulation materials are used in a variety of settings where it isdesired to dampen noise from an external source. For example, soundinsulation materials have been used in applications such as inappliances to reduce the sound emitted into the surrounding areas of ahome, in automobiles to reduce mechanical sounds of the motor and roadnoise, and in office buildings to attenuate sound generated from theworkplace, such as from telephone conversations or from the operation ofoffice equipment. In automobiles, the insulation material also reliesupon thermal shielding properties to reduce or prevent the transmissionof heat from various heat sources in the automobile (e.g., engine,transmission, exhaust, etc.) to the passenger compartment of thevehicle. Acoustical insulation typically relies upon both soundabsorption (i.e., the ability to absorb incident sound waves) andtransmission loss (i.e., the ability to reflect incident sound waves) toprovide adequate sound attenuation.

Conventional acoustical insulation materials include materials such asfoams, compressed fibers, fiberglass batts, felts, and nonwoven webs offibers such as meltblown fibers. Laminates of one or more layers ofinsulation and one or more layers of a rigid material are commonly usedwhen a rigid insulative material is desired. Examples of conventionalacoustical insulation materials are set forth below.

U.S. Pat. No. 5,662,981 to Olinger et al. describes a molded compositeproduct that has a resinous core layer that contains reinforcementfibers (e.g., glass and polymer fibers) and a resinous surface layerthat is substantially free of reinforcement fibers. The surface layermay be formed of thermoplastics or thermoset materials such aspoytretrafluoroethylene, polyethylene terephthalate (PET), polyvinylchloride (PVC), polyphenylene sulfide (PPS), or polycarbonate.

U.S. Pat. No. 5,886,306 to Patel et al. discloses a layered acousticalinsulating web that includes a series of cellulose fiber layerssandwiched between a layer of melt-blown or spun-bond thermoplasticfibers (e.g., polypropylene) and a layer of film, foil, paper, orspunbond thermoplastic fibers.

U.S. Pat. No. 6,669,265 to Tilton et al. describes a fibrous materialthat has a lofty, acoustically insulating portion and a relativelyhigher density skin that may function as a water barrier. The fibrousmaterial includes polyester, polyethylene, polypropylene, polyethyleneterephthalate (PET), glass fibers, natural fibers, and mixtures thereof.

U.S. Pat. No. 6,695,939 to Nakamura et al. discloses an interior trimmaterial that is formed of a substrate and a skin bonded to thesubstrate. The substrate is a mat-like fiber structure that is a blendof thermoplastic and inorganic fibers. The skin is a high melting pointfiber sheet formed from fibers that have a melting point higher than themelting point of the thermoplastic fibers in the substrate. The highmelting point fibers may be polyethylene terephthalate (PET) fibers.

U.S. Patent Publication No. 2003/0039793 A1 to Tilton et al. describes atrim panel insulator for a vehicle that includes a nonlaminateacoustical and thermal insulating layer of polymer fibers. The insulatormay also include a relatively high density, nonlaminate skin of polymerfibers and/or one or more facing layers formed of polyester,polypropylene, polyethylene, rayon, ethylene vinyl acetate, polyvinylchloride, fibrous scrim, metallic foil, and mixtures thereof.

U.S. Patent Publication No. 2004/0002274 A1 to Tilton discloses alaminate material that includes (1) a base layer formed of polyester,polypropylene, polyethylene, fiberglass, natural fibers, nylon, rayon,and blends thereof and (2) a facing layer. The base layer has a densityof from approximately 0.5-15.0 pcf and the facing layer has a density ofbetween about 10 pcf and about 100 pcf.

U.S. Patent Publication No. 2004/0023586 A1 to Tilton et al. and U.S.Patent Publication No. 2003/0008592 to Block et al. disclose a fibrousblanket material that has a first fibrous layer formed of polyester,polypropylene, polyethylene, fiberglass, natural fibers, nylon, and/orrayon and a layer of meltblown polypropylene fibers. A second fibrouslayer may be sandwiched between the first fibrous layer and the layer ofmeltblown fibers. The blanket material may be tuned to provide soundattenuation for a particular product application.

U.S. Patent Publication No. 2004/0077247 to Schmidt et al. describes anonwoven laminate that contains a first layer formed of thermoplasticspunbond filaments having an average denier less than about 1.8 dpf anda second layer containing thermoplastic multicomponent spunbondfilaments having an average denier greater than about 2.3 dpf. Thelaminate has a structure such that the density of the first layer isgreater than the density of the second layer and the thickness of thesecond layer is greater than the thickness of the first layer.

Although there are numerous acoustical insulation products in existencein the art, none of the existing insulation products provide sufficientstructural properties for automotive applications. Thus, there exists aneed for acoustical insulation materials that exhibit superior soundattenuating properties, improved structural and thermal properties, andthat are lightweight and low in cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a multilayercomposite material that may be used in acoustic and semi-structuralapplications. The multilayer composite material is formed of anacoustical composite layer and a first thermal layer. The fibrousmaterial forming the acoustical composite layer includes polymer basedthermoplastic materials such as polyester and polypropylene andreinforcement fibers such as glass fibers. The fibrous material maycontain from 40-60% glass fibers. The first thermal layer is positionedon a first major surface of the acoustical composite layer. The fibrousmaterial forming the first thermal layer includes polymer basedthermoplastic organic materials such as are present in the acousticalcomposite layer. In preferred embodiments, the first thermal layer isformed 100% of polymer fibers. However, bicomponent fibers may beincluded as a component of the fibrous material forming the firstthermal layer in amount of from 10-80% of the total fibers. One or moretypes of polymeric materials may be used to form the first thermallayer. The polymeric materials may have different lengths and diameters.A second thermal layer may optionally be positioned on a second majorsurface of the acoustical composite layer. The acoustical compositelayer and the first and second thermal layers may be non-woven mats ofrandomly oriented fibers and may be formed by air laid, wet-laid, ormeltblown processes.

It is another object of the present invention to provide a method offorming a thermal and acoustic composite material formed of anacoustical composite layer and a first thermal layer. The acousticalcomposite layer is formed of a mixture of thermoplastic polymer fibersand reinforcement fibers and the thermal layer is formed entirely ofthermoplastic polymer fibers. The thermoplastic polymer fibers in thefirst thermal layer may be the same as or different than thethermoplastic polymer fibers in present in the acoustical compositelayer.

In a preferred embodiment, the reinforcement fibers are wet use choppedstrand glass fibers. Wet reinforcement fibers are typically agglomeratedin the form of a bale, package, or bundle of individual glass fibers. Toform the acoustical composite layer, wet reinforcement fibers are openedand at least a portion of the water present in the wet reinforcementfibers is removed. In at least one exemplary embodiment, the bundles ofwet reinforcement fibers are fed into a first opener which at leastpartially opens the bundles and filamentizes the wet reinforcementfibers. The first opener then feeds the opened bundles of wetreinforcement fibers to a condenser to remove water from the wetreinforcement fibers. The reinforcement fibers may then optionally betransferred to a second opener which further filamentizes and separatesthe reinforcement fibers. The thermoplastic polymer fibers may be openedby passing the polymer fibers through an opener. The openers may be baleopeners such as are well-known in the art.

The reinforcement fibers and thermoplastic polymer fibers are thenblended, such as by mixing the fibers together in an air stream. Theblended mixture of reinforcement fibers and polymer fibers may be thentransferred to at least one sheet former where the fibers are formedinto a sheet. The sheet may then be subjected to a needling process inwhich barbed needles are pushed through the fibers of the sheet toentangle the reinforcement fibers and polymer fibers. The sheet may bepassed through a thermal bonder to thermally bond the reinforcementfibers and polymer fibers and form the acoustical composite layer. Thefirst thermal layer is then affixed to a first major surface of theacoustical composite layer.

It is yet another object of the present invention to provide a method offorming a fibrous polymer mat. In this process, no reinforcement fibersare used. Bundles of first polymeric fibers and bundles of secondpolymeric fibers are opened by passing the bundles through first andsecond openers respectively. The opened first and second polymericfibers are then blended and transferred to a sheet former, such as by ablower unit. The sheet may be conveyed to a needle processing apparatusfor mechanical strengthening. A binder resin may be added prior topassing the sheet through a thermal bonder and/or a mechanical needler.The binder resin may be added by any suitable manner known to those ofskill in the art. The resulting fibrous polymer mat may be used as thefirst thermal layer, as well as mats for dash insulators, under carpets,and in trim panels in automobiles.

It is an advantage of the present invention that cycle time, materials,and labor cost needed to provide desired acoustic properties arereduced. Because of the improved structural and thermal properties ofthe multilayer composite material, there is no need to add secondarymaterials to the final acoustic part as is conventionally done toachieve the desired sound attenuation, structural, or insulationcapability. The elimination of these secondary materials reduce theamount of materials needed to form interior acoustic and structuralpanels for automobiles and RVs and eliminates a manufacturing step,thereby increasing overall productivity and decreasing cycle time.

It is another advantage of the present invention that the thermal andacoustic composite material can optimize the properties needed forspecific product applications by altering the weight of the fibers inthe acoustical and insulating later and thermal layer or by changing thetypes of the fibers in each of the layers. In addition, the thickness ofthe formed composite part, the porosity of the formed composite part(e.g., void content), and the air flow path may be controlled bychanging the basis weight of the polymer fibers and/or glass content inthe acoustical composite material.

It is a further advantage of the present invention that the thermal andacoustic composite material may be molded or die-cut to form a desiredacoustical, semi-structural final part in a one step process.

It is yet another advantage of the present invention that when wet usechopped strand glass fibers are used as the reinforcing fiber material,the glass fibers may be easily opened and fiberized with littlegeneration of static electricity due to the moisture present in theglass fibers. In addition, wet use chopped strand glass fibers are lessexpensive to manufacture than dry chopped fibers because dry fibers aretypically dried and packaged in separate steps before being chopped.Therefore, the use of wet use chopped strand glass fibers allowscomposite products to be manufactured at lower costs.

The foregoing and other objects, features, and advantages of theinvention will appear more fully hereinafter from a consideration of thedetailed description that follows. It is to be expressly understood,however, that the drawings are for illustrative purposes and are not tobe construed as defining the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of this invention will be apparent upon consideration ofthe following detailed disclosure of the invention, especially whentaken in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a composite material formed of anacoustical composite layer and a thermal layer according to at least oneexemplary embodiment of the present invention;

FIG. 2 is a flow diagram illustrating steps for using wet reinforcementfibers in a dry-laid process according to one aspect of the presentinvention;

FIG. 3 is a schematic illustration of an air-laid process using wet usechopped strand glass fibers to form an acoustical composite layeraccording to at least one exemplary embodiment of the present invention;

FIG. 4 is a schematic illustration of an air-laid process using twotypes of polymer fibers to form the first thermal layer according to atleast one exemplary embodiment of the present invention; and

FIG. 5 is a schematic illustration of a composite material including athermal layer on a first and second surface of an acoustical compositelayer according to at least one exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are described herein. All references cited herein,including published or corresponding U.S. or foreign patentapplications, issued U.S. or foreign patents, or any other references,are each incorporated by reference in their entireties, including alldata, tables, figures, and text presented in the cited references.

In the drawings, the thickness of the lines, layers, and regions may beexaggerated for clarity. It will be understood that when an element suchas a layer, region, substrate, or panel is referred to as being “on”another element, it can be directly on the other element or interveningelements may also be present. The terms “top”, “bottom”, “side”, and thelike are used herein for the purpose of explanation only. It is to benoted that like numbers found throughout the figures denote likeelements. The terms “sheet”, “mat”, “veil”, and “web” may be usedinterchangeably herein.

The invention relates to a multilayer acoustic material that is formedof (1) a first composite layer that includes a polymer basedthermoplastic material (e.g., polypropylene) and reinforcement fibers(e.g., glass fibers) and (2) a second layer of organic fibers (e.g.,polyethylene terephthalate). The multilayer composite material may beutilized in a number of non-structural acoustical applications such asin appliances, in office screens and partitions, in ceiling tiles, inbuilding panels, and in semi-structural applications such as inautomobiles (e.g., headliners, hood liners, floor liners, trim panels,parcel shelves, sunshades, instrument panel structures, door inners, andthe like), and in wall panels and roof panels of recreational vehicles(RV's).

A multilayer thermal and acoustic composite material 10 formed of anacoustical composite layer 12 and a first thermal layer 14 isillustrated in FIG. 1. It is to be understood that the nomenclature forthe acoustical composite layer 12 and the first thermal layer 14 areused for ease of discussion herein and that both the acousticalcomposite layer 12 and the first thermal layer provide acoustical andthermal insulating properties. In addition, at least the acousticalcomposite layer 12 provides structural or semi-structural properties tothe final acoustical product.

The fibrous material forming the acoustical composite layer 12 includespolymer based thermoplastic materials such as, but not limited to,polyester, polyethylene, polypropylene, polyethylene terephthalate(PET), polyphenylene sulfide (PPS), polyvinyl chloride (PVC), ethylenevinyl acetate/vinyl chloride (EVA/VC) fibers, lower alkyl acrylatepolymer fibers, acrylonitrile polymer fibers, partially hydrolyzedpolyvinyl acetate fibers, polyvinyl alcohol fibers, polyvinylpyrrolidone fibers, styrene acrylate fibers, polyolefins, polyamides,polysulfides, polycarbonates, rayon, nylon, and mixtures thereof. Thus,one or more polymers may be present in the acoustical composite layer12. Preferably, the polymer fibers are from approximately 6-75 mm inlength, and are more preferably from 18-50 mm in length. Additionally,the polymer fibers may have a weight per length of from 3-30 denier, andpreferably have a weight per length of from 3-7 denier. Thethermoplastic polymer fibers may have varying lengths (e.g., aspectratios) and diameters within the acoustical composite layer 12. Thepolymer fibers may be present in the acoustical composite layer 12 in anamount of from 40-80% by weight, and are preferably present in an amountof from 40-60% by weight.

The polymer fibers may be functionalized with acidic groups, forexample, by carboxylating with an acid such as a maleated acid or anacrylic acid, or the polymer fibers may be functionalized by adding ananhydride group or vinyl acetate. The polymeric thermoplastic materialmay be in the form of a flake, granule, or a powder rather than in theform of a polymer fiber. A resin in the form of a flake, granule, and/ora powder may be added in addition to the polymer fibers.

In addition, the fibrous material forming the acoustical composite layer12 includes reinforcing fibers such as, but not limited to, glassfibers, natural fibers, metal fibers, ceramic fibers, mineral fibers,carbon fibers, graphite fibers, or combinations thereof to meet thespecific performance requirements of a particular application.Preferably, the reinforcing fiber material is glass fibers. Any type ofglass fibers, such as A-type glass fibers, C-type glass fibers, E-typeglass fibers, S-type glass fibers, or modifications thereof, may beincluded as a reinforcing fiber material in the acoustical compositelayer 12. The term “natural fiber” as used in conjunction with thepresent invention refers to plant fibers extracted from any part of aplant, including, but not limited to, the stem, seeds, leaves, roots, orbast. Examples of natural fibers suitable for use as the reinforcingfiber material include cotton, jute, bamboo, ramie, hemp, flax, andcombinations thereof.

The fibrous material may contain from 20-60%, and preferably from40-60%, of the natural, glass, or other reinforcing fibers. Thereinforcing fibers may have diameters ranging from approximately 11-25microns and lengths from approximately 10-100 mm. In preferredembodiments, the reinforcing fibers have diameters of from 12-18 micronsand lengths of from 25-50 mm. As with the thermoplastic polymer fibers,the reinforcing fibers may have varying lengths and diameters within theacoustical composite layer 12.

The acoustical composite layer 12 may be formed of an air-laid,wet-laid, or meltblown non-woven mat or web of randomly orientedthermoplastic fibers and glass fibers. In at least one exemplaryembodiment, the acoustical composite layer 12 is formed by a wet-laidprocess. For example, chopped glass fibers and thermoplastic fibers, maybe dispersed in an aqueous solution that contains a binder as well asdispersants, viscosity modifiers, defoaming agents, and/or otherchemical agents and agitated to form a slurry. The thermoplastic andglass fibers located in the slurry may then be deposited onto a movingscreen whereby water is removed to form a mat. Optionally, the mat isdried in an oven. The mat may then be immersed into a binder compositionwhere the binder impregnates the mat. The mat is then dried to removeany remaining water and to cure the binder. The resulting non-woven mat(e.g., acoustical composite layer 12) is an assembly of dispersedthermoplastic fibers and glass filaments.

Alternatively, the acoustical composite layer 12 may be formed by usingwet use chopped strand glass fibers (WUCS) in a dry laid process asdescribed and disclosed in the parent application, U.S. patentapplication Ser. No. 10/688,013, filed on Oct. 17, 2003 to Enamul Haqueentitled “Development Of Thermoplastic Composites Using Wet Use ChoppedStrand Glass In A Dry Laid Process.” Such a process, as generallyillustrated in FIG. 2, includes opening the reinforcement fibers andpolymer (resin) fibers (step 100), blending the reinforcement and resinfibers (step 110), forming the reinforcement and resin fibers into asheet (step 120), optionally needling the sheet to give the sheetstructural integrity (step 130), and thermal bonding the sheet (step140).

Turning now to FIG. 3, the opening of the wet reinforcement fibers andthe polymer fibers can best be seen. Although FIG. 3 depicts the openingof wet use chopped strand glass fibers (WUCS), a preferred wetreinforcement fiber, any suitable wet reinforcement fiber identified byone of skill in the art could be utilized in the illustrated process.Wet reinforcement fibers, such as are used in the present invention, aretypically agglomerated in the form of a bale, package, or a bundle ofindividual glass fibers. The term “bundle” as used herein is meant toindicate any type of agglomeration of wet reinforcement fibers, whichwould be easily identified and understood by those of ordinary skill inthe art. Wet use chopped strand glass fibers used as the reinforcementfibers can be formed by conventional processes known in the art.Preferably, the wet use chopped strand glass fibers have a moisturecontent of from 5-30%, and more preferably have a moisture content offrom 5-15%.

To open the wet use chopped strand glass fibers, the WUCS glass fibers200, typically in the form of a bale, package, or bundle of individualglass fibers, are fed into a first opener 210 which at least partiallyopens and filimentizes (e.g., individualizes) the WUCS glass fibers 200.The first opener 210 may then dose or feed the WUCS glass fibers 200 toa condenser 220 where water is removed from the WUCS glass fibers 200.In exemplary embodiments, greater than 70% of the free water, e.g.,water that is external to the glass fibers, is removed. Preferably,however, substantially all of the water is removed by the condenser 220.It should be noted that the phrase “substantially all of the water” asit is used herein is meant to denote that all or nearly all of the freewater is removed.

Once the WUCS glass fibers 200 have passed through the condenser 220,the WUCS glass fibers 200 may then be passed through a second opener230. The second opener 230 further filimentizes and separates the WUCSglass fibers 200.

To open the polymer fibers 240, the polymer fibers 240 may be passedthrough a third opener 250 where the polymer fibers 240 are opened andfilamentized. In alternate embodiments where the resin is in the form ofa flake, granule, or powder, the third opener 250 may be replaced withan apparatus suitable for distributing the polymer fibers 240 to theblower unit 260 for mixing with the WUCS glass fibers 200. A suitableapparatus would be easily identified by those of skill in the art. Inembodiments where a resin in the form of a flake, granule, or powder isused in addition to the polymer fibers 240, the apparatus distributingthe flakes, granules, or powder does not replace the third bale opener250. Alternatively, a resin powder, flake, or granule may be added priorthermal bonding in the thermal bonder 290 in addition to, or in placeof, the polymer fibers 240.

Other types of fibers such as chopped roving, dry use chopped strandglass (DUCS), A-type, C-type, E-type, or S-type glass fibers, naturalfibers (e.g., jute, hemp, and kenaf), aramid fibers, metal fibers,ceramic fibers, mineral fibers, carbon fibers, graphite fibers, polymerfibers, or combinations thereof can be opened and filamentized byadditional openers (not shown) depending on the desired composition ofthe acoustical composite layer 12. These fibers can be added to the airstream in the blower unit 260 and mixed with the WUCS glass fibers 200as described below with respect to the polymer fibers 240. When suchfibers are added, it is preferred that from about 10-30% of the fibersin the air stream consist of these additional fibers.

The first, second, and third openers (210, 230, 250) are preferably baleopeners, but may be any type of opener suitable for opening the bundleof wet reinforcement fibers. The design of the openers depends on thetype and physical characteristics of the fiber being opened. Suitableopeners for use in the present invention include any conventionalstandard type bale openers with or without a weighing device. The baleopeners may be equipped with various fine openers and may optionallycontain one or more licker-in drums or saw-tooth drums. The bale openersmay be equipped with feeding rollers or a combination of a feedingroller and a nose bar. The condenser 220 may be any known drying orwater removal device known in the art, such as, but not limited to, anair dryer, an oven, rollers, a suction pump, a heated drum dryer, aninfrared heating source, a hot air blower, or a microwave emittingsource.

After the WUCS glass fibers 200 and the polymer fibers 240 have beenopened and filamentized, they may be transferred to a blower unit 260where the WUCS glass fibers 200 and polymer fibers 240 are blendedtogether in an air stream (step 110 of FIG. 2). The blended WUCS glassfibers 200 and polymer fibers 240 may then be transferred by the airstream from the blower unit 260 to a first sheet former 270 where thefibers are formed into a sheet (step 120 of FIG. 2). In one exemplaryembodiment of the invention, the opened WUCS glass fibers 200 andpolymer fibers 240 are transferred from the blower unit 260 to a fillingbox tower 265 to volumetrically feed the WUCS glass fibers 200 andpolymer fibers 240 into the first sheet former 270, such as by anelectronic weighing apparatus. The filling box tower 265 may be locatedin the first sheet former 270 or it may be positioned external to thefirst sheet former 270. Additionally, the filling box tower 265 mayinclude baffles to further blend and mix the WUCS glass fibers 200 andpolymer fibers 240 prior to entering the first sheet former 270.

Alternatively, the blended WUCS glass fibers 200 and polymer fibers 240are blown onto a drum or series of drums covered with fine wires orteeth to comb the fibers into parallel arrays prior to entering thefirst sheet former 270 (not shown), as in a carding process.

In at least one exemplary embodiment, the sheet formed by the firstsheet former 270 is transferred to a second sheet former 275. The secondsheet former 275 permits the sheet to have a substantially uniformdistribution of the WUCS glass fibers 200 and polymer fibers 240. Inaddition, the second sheet former 275 permits the acoustical compositelayer 12 to have high structural integrity. In particular, theacoustical composite layer 12 formed may have a weight distribution offrom 100-3000 g/m², with a preferred weight distribution range fromabout 600 to 2000 g/m².

The first and second sheet formers 270, 275 may include at least onelicker-in drum having two to four sieve drums. Depending on thereinforcement fibers used, the first and second sheet formers 270, 275may be equipped with one or more of the following: a condenser, adistribution conveyor, a powder strewer, and/or a chip strewer. A sheetformer having a condenser and a distribution conveyor is typically usedto achieve a higher fiber feed into the filling box tower 265 and anincreased volume of air through the filling box tower 265. In order toachieve an improved cross-distribution of the opened fibers, thedistributor conveyor can run transversally to the direction of thesheet. As a result, the opened fibers are transferred from the condenserand into the filling box tower 265 with little or no pressure.

The sheet exiting the first sheet former 270 and the second sheet former275 may optionally be subjected to a needling process in which needlesare pushed through the fibers of the sheet to entangle the WUCS glassfibers 200 and polymer fibers 240 (step 130 of FIG. 2). The needlingprocess may occur in a needle felting apparatus 280. The needle feltingapparatus 280 may include a web feeding mechanism, a needle beam with aneedleboard, barbed felting needles ranging in number from about 500 permeter to about 7,500 per meter of machine width, a stripper plate, a bedplate, and a take-up mechanism. Mechanical interlocking of the WUCSglass fibers 200 and polymer fibers 240 is achieved by passing thebarbed felting needles repeatedly into and out of the sheet. An optimalneedle selection for use with the particular reinforcement fiber andpolymer fiber chosen for use in the inventive process would be easilyidentified by one of skill in the art.

Either after the sheet forming step 120 (FIG. 2) or the optionalneedling step 130 (FIG. 2), the sheet may be passed through a thermalbonder 290 to thermally bond the WUCS glass fibers 200 and polymerfibers 240. In thermal bonding, the thermoplastic properties of thepolymer fibers are used to form bonds with the reinforcement fiber(e.g., WUCS glass fibers 200) upon heating. The thermal bonder 290 mayinclude any known heating and bonding method known in the art, such asoven bonding, oven bonding using forced air, infrared heating, hotcalendaring, belt calendaring, ultrasonic bonding, microwave heating,and heated drums. Optionally, two or more of these bonding methods maybe used in combination to bond the WUCS glass fibers 200 and polymerfibers 240 in the sheet. The temperature of the thermal bonder 290 mayrange from approximately 100° C. to approximately 250° C., depending onthe melting point of the particular polymer fiber(s) used.

Although the thermoplastic properties of the polymer fibers 240 can beused to bond the WUCS glass fibers 200 and polymer fibers 240, singlecomponent binding fibers, bicomponent binding fibers, and/or powderedpolymers may be added to the sheet to further bond the WUCS glass fibers200 and polymer fibers 240. Typical examples of such fibers includepolyester fibers, polyethylene fibers, and polypropylene-polyethylenefibers. Such fibers may be added during the initial blending of the WUCSglass fibers 200 and the polymer fibers 240 in the blower unit 260.

Another method that may be used to increase the strength of the sheetafter it exits either the first sheet former 270 or the second sheetformer 275 is chemical bonding. In chemical bonding, a bonding agent isapplied to a sheet or web to bond the reinforcement fibers and resinfibers. Liquid based bonding agents, powdered adhesives, foams, and, insome instances, organic solvents can be used as the chemical bondingagent. If the bonding agent is in powdered or flaked form, it can beadded to the sheet prior to the sheet entering the thermal bonder 290.Suitable examples of chemical bonding agents include, but are notlimited to, acrylate polymers and copolymers, styrene-butadienecopolymers, vinyl acetate ethylene copolymers, and combinations thereof.For example, polyvinyl acetate (PVA), ethylene vinyl acetate/vinylchloride (EVA/VC), lower alkyl acrylate polymer, styrene-butadienerubber, acrylonitrile polymer, polyurethane, epoxy resins, polyvinylchloride, polyvinylidene chloride, and copolymers of vinylidene chloridewith other monomers, partially hydrolyzed polyvinyl acetate, polyvinylalcohol, polyvinyl pyrrolidone, polyester resins, and styrene acrylatemay be used as a bonding agent. The chemical bonding agent can beapplied uniformly by impregnating, coating, or spraying the sheet. Whenthe sheet containing the bonding agents is passed through the thermalbonder 290, the bonding agent further bonds the WUCS glass fibers 200and the polymer fibers 240. Although the temperature requirements forinitiating chemical bonding is generally lower than the temperaturerequirements for thermally bonding the reinforcement fibers and theresin fibers, the chemical bonding process is not as desirable asthermal bonding because it requires the removal of excess bonding agentsand further drying of the sheet.

The fibrous material forming the first thermal layer 14 includes polymerbased thermoplastic organic materials such as, but not limited to,polyester, polyethylene, polypropylene, polyethylene terephthalate(PET), polyphenylene sulfide (PPS), polyvinyl chloride (PVC),polyolefins, polyamides, polysulfides, polycarbonates, and mixturesthereof. One or more types of polymeric materials may be used to formthe first thermal layer 14. The polymer(s) forming the first thermallayer 14 may have the same or different lengths and/or diameters. Forexample, the first thermal layer 14 may be formed of a single polymericfibrous material (e.g., PET) in which the polymer fibers have differentlengths and/or diameters. As another example, the first thermal layer 14may be formed of two or more different polymers, and each of thepolymers may have the same lengths and diameters, or, alternatively, thepolymers may have different lengths and/or diameters. The acousticalbehavior of the composite product may be fine tuned by altering thelengths and denier of the polymer fibers. In addition, the ratio of thepolymeric fibrous materials present in the first thermal layer 14 can bevaried to achieve specific acoustic properties. The polymer fibers inthe first thermal layer 14 may be from approximately 2-30 deniers indiameter, preferably between 3-7 deniers, and may have a length of from6-75 mm, preferably from 18-50 mm. In preferred embodiments, the lengthof the polymer fibers in the first thermal layer 14 is the substantiallythe same length as the reinforcement fibers present in the acousticalcomposite layer 12.

Additionally, the fibrous material of the first thermal layer 14 mayinclude heat fusible fibers such as bicomponent fibers. Bicomponentfibers include two polymers combined to form fibers that have a core ofone polymer and a surrounding sheath of the other polymer. Whenbicomponent fibers are used as a component of the first thermal layer12, the bicomponent fibers may be present in an amount of from 10-80% ofthe total fibers.

The first thermal layer 14 is a non-woven mat that may be formed by anair-laid, wet-laid, or meltblown process, and is desirably formed of100% polymer based thermoplastic materials such as described above.Preferably, the first thermal layer 14 is formed by an air-laid process.For example, an air-laid mat of thermoplastic fibers may be made bymelting a polymeric material within a melter or die and extruding themolten polymeric material through a plurality of orifices to formcontinuous filaments. As the polymer filaments exit the orifices, theyare introduced directly into a high velocity air stream which attenuatesthe filaments and forms discrete, individual polymeric fibers. Thepolymeric fibers may then be cooled and collected on a moving airpermeable conveyor or screen to form the first thermal layer 14.

One exemplary embodiment of the formation of the first thermal layer 14using two polymer fibers in a dry-laid process is shown in FIG. 4. It isto be appreciated that additional polymeric fibers may be used to formthe first thermal layer 14 and that the depiction of two polymer fibersin FIG. 4 is for illustration only. First polymeric fibers 300 andsecond polymeric fibers 400 may be opened by passing the first polymericfibers 300 and the second polymeric fibers 400, typically in the form ofa bale, package, or a bundle of individual fibers, through a firstopener 210 and a second opener 410 respectively. The first polymericfibers 300 and second polymeric fibers 400 may be the same or different,and may have different lengths and/or diameters from each other asdescribed above. The polymeric fibers 300, 400 are then conveyed by ablower unit 260 to a first sheet former 270. Alternatively, the firstand second polymeric fibers 300, 400 may be conveyed to a filling boxtower 265 to volumetrically fed the first and second polymeric fibers300, 400 to the first sheet former 270. The sheet exiting the sheetformer 270 may then optionally be conveyed to a second sheet former (notshown) and/or a needle felting apparatus 280 (not shown) for mechanicalstrengthening.

A binder resin 350 may be added prior to passing the sheet through thethermal bonder 290. The binder resin 350 may be added by any suitablemanner, such as, for example, a flood and extract method or by sprayingthe binder resin 350 on the sheet. Any binder resin capable of bindingthe polymeric fibers 300, 400 may be used. Suitable examples includesingle and bicomponent fibers or powders. Further, the amount of binderadded may be varied depending of the type of mat desired. The sheet isthen passed through a thermal bonder 290 to cure the binder resin 350and provide structural integrity to polymeric fibers 300, 400.Alternatively, a catalyst such as ammonium chloride, p-toluene, sulfonicacid, aluminum sulfate, ammonium phosphate, or zinc nitrate may be usedto improve the rate of curing and the quality of the cured binder resin.

The first thermal layer 14 is positioned on a major surface of theacoustical composite layer 12, and may be attached to the acousticalcomposite layer 12 such as by a nip-roll system or by using a laminator.In addition, resin tie layers such as Plexar™ (commercially availablefrom Quantum Chemical), Admer™ (commercially available from MitsuiPetrochemical), and Bynel™ (an anhydride modified polyolefincommercially available from DuPont), spray-on adhesives, pressuresensitive adhesives, ultrasonics, vibration welding, or other commonlyused fixation technologies may be used to hold the two thermoplasticlayers together. It is preferred that the first thermal layer 14 isattached to the acoustical composite layer 12 in-line to improvemanufacturing efficiency.

Optionally, a second thermal layer 16 may be positioned on a secondmajor surface of the acoustical composite layer 12 as shown in FIG. 5.The second thermal layer 16 is formed of 100% thermoplastic organicpolymers such as described above with respect to the first thermal layer14, and may be the same as, or different than, the first thermal layer14. Non-limiting examples of the polymer based thermoplastic, organicmaterials used to form the second thermal layer 16 include polyester,polyethylene, polypropylene, polyethylene terephthalate (PET),polyphenylene sulfide (PPS), polyvinyl chloride (PVC), polyolefins,polyamides, polysulfides, polycarbonates, and combinations thereof. Thesecond thermal layer 16 may be bonded to the acoustic and insulatinglayer 12 by a nip-roll system, by a laminator, or by resin tie layerssuch as described above.

In addition, the acoustical composite material 10 may also include afacing layer (not shown) on one or both thermal layers 14,16. The facinglayer may be in the form of a film such as a copolymer of ethylene-vinylacetate (EVA) or it may be a textile fabric formed of a syntheticpolymer such as, but not limited to, polyethylene terephthalate (PET) ornylon. In addition, the facing layer may be vinyl, leather, orpaper-based. The facing layer may assist in altering the acousticalproperties of the acoustical composite material 10 so that it can betuned to meet the needs of a particular application. In addition,depending on the material of the facing layer, the facing layer mayimprove physical properties of the acoustical composite material 10 suchas, but not limited to, water permeability or non-permeability, abrasionresistance, and/or heat resistance.

The process of manufacturing the acoustical composite layer 12, thefirst thermal layer 14, and the optional second thermal layer 16 may beconducted either in-line, i.e., in a continuous manner, or in individualsteps. Preferably, the process is conducted in-line. Moreover, anyadditional process steps such as adding specialty films, scrims, and/orfabrics are considered within the scope of the invention.

The acoustical composite material 10 may be heated in a forced-air,convection, or infra-red oven to cause the acoustical composite layer 12and the first thermal layer 14 to loft or expand. The lofted thermal andacoustic composite material 10 may then be molded (e.g., thermo-formedor thermo-stamped) or die-cut with or without a surface material to forma desired acoustical, semi-structural final part, such as, for example,headliners, hood liners, floor liners, trim panels, parcel shelves,sunshades, instrument panel structures, door inners, or wall panels orroof panels of recreational vehicles in a one step process.

The thermal and acoustic composite material 10 of the present inventionreduces the cycle time, materials, and labor cost needed to providedesired acoustic properties. For example, when automotive interiorpanels or load floors are conventionally manufactured, additional layersof materials such as cotton shoddy or polymeric fiber based mats areadded to the panels to reduce the noise in the passenger compartment.Because of the high acoustical performance of the composite material 10,there is no need to add a secondary material to the final acoustic part(e.g., interior trim panels or headliners) to achieve the desired soundattenuation. In addition, in conventional structural applications, suchas interior side walls of recreational vehicles, foam is added behindthe side panel to increase insulation capability. Because of theimproved structural and thermal properties of the composite material 10,the use of such foams is unnecessary. The elimination of these secondarymaterials reduces the amount of materials needed to form such interioracoustic and structural panels for automobiles and RVs and eliminates amanufacturing step (i.e., installing the secondary materials), therebyincreasing overall productivity and decreasing cycle time.

In addition, the thermal and acoustic composite material 10 provides theability to optimize the properties needed for specific applications byaltering the weight of the fibers in the different layers, by changingthe glass content and/or length or diameter of the glass, by alteringthe polymeric fiber length or denier, or by changing the formulations ofthe fibers in each of the layers during the manufacturing of theproduct. The thickness of the formed composite part, porosity of theformed composite part (e.g., void content), and the air flow path may becontrolled by changing the basis weight of the polymer fibers and/orglass content of the thermal and acoustic composite material 10. Forexample, increasing the weight and glass content of the thermal andacoustic composite material 10 may increase the thickness of the finalacoustical part, which, in turn, may increase the porosity of the finalproduct. In addition, the direction of the glass fibers in theacoustical composite layer 12 may be directionally positioned in anair-laid process to change the air flow path and achieve desiredacoustical properties or to tune the composite material 10 to meet theneeds of a particular application. Typically, glass fibers are laid inan X-Y direction. However, adding a z-directionality to the layers 12,14 increase the resistance to flow and improves sound absorptionproperties.

The composite material 10 forms a final product that demonstratesimproved structural and thermal properties. Although not wishing to bebound by theory, the improved structural properties (e.g., flexural andtensile properties) of the final part are believed to be attributed tothe various combinations of polymeric fibers and glass fibers ofdifferent physical properties (e.g., lengths and diameters) in theacoustical composite layer 12. It is also believed that the improvedthermal properties of the final part may be attributed polymeric fibersin the thermal layer 14. The thermal layer 14 provides improved end usetemperature capability (e.g., heat deflection temperature) andacoustical properties.

It is an advantage of the present invention that when wet use choppedstrand glass fibers are used as the reinforcing fiber material, theglass fibers may be easily opened and fiberized with little generationof static electricity due to the moisture present in the glass fibers.In addition, wet use chopped strand glass fibers are less expensive tomanufacture than dry chopped fibers because dry fibers are typicallydried and packaged in separate steps before being chopped. Therefore,the use of wet use chopped strand glass fibers allows the compositeproduct to be manufactured with lower costs.

It is a further advantage of the present invention that the thermal andacoustic composite material may be molded (e.g., thermo-formed orthermo-stamped) or die-cut to form a desired acoustical, semi-structuralfinal part in a one step process.

It is another advantage of the present invention that the thermal andacoustic composite material optimizes the properties needed for specificapplications by altering the weight of the fibers in the differentlayers or by changing the formulations of the fibers in each of thelayers during the manufacturing of the product. The thickness of theformed composite part, porosity of the formed composite part (e.g., voidcontent), and the air flow path may be controlled by changing the basisweight of the polymer fibers and/or glass content of the acousticalcomposite material.

The invention of this application has been described above bothgenerically and with regard to specific embodiments. Although theinvention has been set forth in what is believed to be the preferredembodiments, a wide variety of alternatives known to those of skill inthe art can be selected within the generic disclosure. The invention isnot otherwise limited, except for the recitation of the claims set forthbelow.

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 23. A method of forming afibrous polymer mat comprising the steps of: at least partially openinga bundle of first polymeric fibers; at least partially opening a bundleof second polymeric fibers; blending said at least partially openedfirst and second polymeric fibers to form a mixture of said at leastpartially opened first and second polymeric fibers; forming said mixtureinto a sheet; bonding said first and second polymeric fibers to formsaid fibrous polymer mat.
 24. The method of claim 23, further comprisingthe step of: adding a binder resin to said sheet prior to said bondingstep.
 25. The method of claim 24, further comprising the step of:conveying said at least partially opened first and second polymericfibers to a filling box tower prior to said forming step.
 26. The methodof claim 24, wherein said forming step comprises the step of: passingsaid mixture through at least one sheet former.
 27. The method of claim24, further comprising the step of: needling said first polymeric fibersand said second polymeric fibers prior to said bonding step tomechanically strengthen said fibrous polymer mat.